A BICYCLE shed is a building; Lincoln Cathedral is a piece of architecture.'' This is how the architectural historian Nikolaus Pevsner began his classic book ``Outline of European Architecture'' (still in print 50 years after first publication).
But what about a rail shed?
Rail sheds can quite definitely be architecture. Pevsner himself considered some of the great iron structures constructed by the Victorians over their major rail terminals to be much more than mere buildings or just engineering.
What he would have thought of the stimulating new International Terminal at Waterloo Station, London, can, of course, only be guessed. But surely it would have been approval. The critic for Architectural Review, Peter Davey, is, at any rate, far from being alone in his enthusiasm for this sinuous - indeed twisting - 1,312-foot arched tunnel of steel and glass. The shed covers five tracks that lead to and from the recently completed Channel Tunnel 70 miles away.
From this point south of the River Thames but close to the center of London, passengers will be three hours' ride from Paris. The first limited services are expected to begin in July. Eventually trains will arrive and depart every 10 minutes, and there will also be another high-speed train link to and from the Chunnel that will terminate at St. Pancras Station in the north part of London. From St. Pancras, they say, it will take under 2-1/2 hours to reach Paris.
But that is at least four or five years away. In the meantime, the Waterloo Terminal, which has all the feel of an airport in competition with real airports, is the impressive launching pad for a new kind of London-to-Paris (and London-to-Brussels) travel. It is designed to handle up to 15 million passengers a year.
Mr. Davey describes the Waterloo Terminal (architects: Nicholas Grimshaw and Partners) in glowing terms: ``a walk down the shed, with the fine pattern of the faceted skin on its light steel lattices gently curving in three dimensions overhead, is one of the most moving and dramatic experiences in the history of glass and metal buildings.''
It is the sort of heroically exciting project that few architects have the opportunity to design, and then only once in a lifetime. Quite consciously, it is a 1990s concept to vie with the kind of rail stations built when trains represented all that was advanced in public transport. Ironically, it magnificently ignores the fact that rail services in Britain are today as ailing and inefficient as anyone can remember because the government shows more concern for road than rail. Opened by Queen Elizabeth, however, and admired on all sides, the Waterloo Terminal looks to have an optimistic future.
The attention of passengers leaving London is drawn immediately toward the complex roof structure, which - long before they will be entering the tunnel under the ocean channel between England and France - is a tunnel experience in itself. It is made even more dramatic by the way it curves so that its furthest point is hidden from view, and by the fact that the tracks and platforms grow narrower and closer as the trains depart. Visually this exaggerated perspective intensifies the sense of recession and directional force that is such a compelling part of rail lines anyway. Travelers are not only about to leave on a journey, they have an aesthetic send-off.
The roof of this train-shed-tunnel at Waterloo is not under ground or ocean, but under sky. It is light in both senses of the word, illuminating the curving platforms beneath it and emphasizing with exultation the poetry of departure and arrival, of momentum and streamlined grace that once, in a less cynical time, made people feel that travel on earth was not far from travel to the moon.
The new terminal was not built on a large open site. It is what the architects call a constrained urban site, squeezed alongside the existing Waterloo Station, which is reputed to be Europe's busiest rail station: a hive of commuter bees.
The new shed covers existing lines, one of which is a single track tight against the western side. Another limiting requirement was that it should not be higher than the adjacent station's roof.
The result of such constraints imposed upon the terminal's design have been turned to distinct advantage. It is perhaps these limits that have forced on it its unusual, eccentric form. The roof structure is of three-pin arches, but these arches rise much more steeply on one side than the other, and the meeting point of these two sides is off-center. This lack of symmetry is therefore in addition to the curving and tapering of the structure along its length, and the whole effect is one of an almost organic articulation. It has been compared to a caterpillar.
Although its materials are the standard ones of modernist architecture - glass, steel, and concrete - it has none of the stiff linear quality that such materials have so frequently seemed to impose of the 20th-century architectural imagination.
Instead, here is a building that is almost like the rib cage of an animal, the experience of walking or standing in it is like that of Jonah inside the whale.
The architects have added even further interest to the contrast between the tight arching up-curve of the ``minor trusses'' on the west side of the shed and the flatter, stretching curve of the ``major trusses'' on the east. They have made the minor steel trusses above and outside the cladding skin of glass, while the major trusses are inside with the glass panels sitting on top of them. In this way there is a fascinating interplay of inner and outer structure.
Extreme expense might have been incurred if a standard glazing system had been used on this sinuous roof. The roof's varying turns and widths would have dictated thousands of differently sized-and-shaped components. Instead, a loose-fit approach was taken. Only a limited number of different-sized glass sheets were manufactured, and each was separately framed.
These framed sheets were overlapped top and bottom like roof tiles. Their sides are joined (and weather-proofed) by means of neoprene (a kind of rubber) gaskets that can flex and expand.
Though the roof is undoubtedly what visitors will most remember, it is only the tip of this project's iceberg, a mere 10 percent of the cost. Floors below the tracks provide extensive arrival-and-departure areas with all the atmosphere of an airport, and a parking area in the basement.
Ticket, security, and passport checks are all dealt with in linear progression on the levels below the platforms and tracks. Elevators, escalators, and moving sidewalks link arrival-and-departure floors to the platforms - and also to the subway (Underground) and the old Waterloo Station or street.
One early plan was to let the light from the splendid roof filter through to these lower areas by means of glass floors. That had to be abandoned, which is a pity. But this loss of originality is to some degree compensated for by the ubiquitous attention to detail by the architects.
They have designed virtually every inch of this new building except for the Eames seating. Even the toilets have been praised. And even the finish of the concrete is quite beautiful.